(a) Field of the Invention
The present invention relates to a recording circuit arrangement for use in driving a magnetic recording head in a magnetic recording apparatus employing the AC biasing system.
(b) Description of the prior art
Magnetic recording apparatus such as magnetic tape recorders usually employ the so-called AC biasing system in recording signals. Such known AC biasing system is arranged so that an AC biasing signal having a frequency higher than that of recording signal for recording is applied to the magnetic recording head together with said recording signal, to thereby improve frequency response and to minimize distortion and noise.
FIG. 1 shows a typical example of a known recording circuit arrangement used for driving the magnetic recording head in a magnetic recording apparatus. More particularly, the recording signal supplied from a recording signal source 1 is amplified at an amplifier 2. This amplified recording signal is fed to a magnetic recording head 5 via a trap network formed by a parallel connection of a coil 3 and a capacitor 4. An AC biasing signal source 7 is coupled to the recording head 5 via a trimmer capacitor 8 for bias-level adjustment. Thus, the magnetic recording head 5 is driven by both the recording signal and the AC biasing signal which are superposed one upon another, so that the recording signal is recorded, in accordance with the principle of the AC biasing system, on a magnetic recording medium, such as magnetic tape, provided on the recording apparatus. The recording signal may be an audio signal of 20 to 20,000 Hz, and in such instance the AC biasing signal supplied from the signal source 7 may be an AC signal of 30 to 100 kHz.
The trap network mentioned above is a parallel resonance circuit formed, by the coil 3 and the capacitor 4, and intended to prevent the undesirable flow of the AC biasing signal back to the amplifier 2. Absent such a trap the AC biasing signal, which has a frequency higher than that of the recording signal, would cause problems such as circuit saturation in the amplifier 2. On the other hand, the trap network can constitute a cause of distortion of the recording signal which passes therethrough, leading to degraded fidelity of the recording signals. Thus, ideally it is desirable to arrange that the parallel connection be omitted, and that the amplifier 2 be connected directly to the magnetic recording head 5. This arrangement, however, would lead to the above-mentioned introduction of the output of the AC biasing signal source 7 into the amplifier 2 resulting in the saturation of the latter.